Synthesis of a NaYF4:Yb,Er upconversion film on a silicon substrate and its tribological behavior

Abstract

In this work, amino-functionalized NaYF₄:Yb,Er upconversion nanoparticles (UCNPs) were synthesized by a hydrothermal method. Then a simple self-assembly method was carried out to prepare a NaYF₄:Yb,Er upconversion (UC) film on a silicon (Si) substrate, using γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560) as an intermediate coupling agent. The chemical composition and surface morphology of the UC film were characterized using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), water contact angle (WCA), and scanning electron microscopy (SEM) measurements. Furthermore, the tribological properties of the UC film were investigated by a UMT tester. The results indicate that the UC film has been successfully prepared on the Si substrate by the formation of chemical bonds and its lifetime is about five times longer than that of the NaYF₄:Yb,Er UCNPs on a bare Si substrate. This work provides a facile way to synthesize a NaYF₄:Yb,Er UC film with robust adhesion to the substrate, which can be applicable for other UC films.